Re: [PATCH v19 036/130] KVM: TDX: x86: Add ioctl to get TDX systemwide parameters

[Huang, Kai]

On 26/02/2024 9:25 pm, Yamahata, Isaku wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> Implement an ioctl to get system-wide parameters for TDX.  Although the
> function is systemwide, vm scoped mem_enc ioctl works for userspace VMM
> like qemu and device scoped version is not define, re-use vm scoped
> mem_enc.

-EPARSE for the part starting from "and device scoped ...".

Grammar check please.

> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
> v18:
> - drop the use of tdhsysinfo_struct and TDH.SYS.INFO, use TDH.SYS.RD().
>    For that, dynamically allocate/free tdx_info.
> - drop the change of tools/arch/x86/include/uapi/asm/kvm.h.
>
> v14 -> v15:
> - ABI change: added supported_gpaw and reserved area.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
>   arch/x86/include/uapi/asm/kvm.h | 17 ++++++++++
>   arch/x86/kvm/vmx/tdx.c          | 56 +++++++++++++++++++++++++++++++++
>   arch/x86/kvm/vmx/tdx.h          |  3 ++
>   3 files changed, 76 insertions(+)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 9ea46d143bef..e28189c81691 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -604,4 +604,21 @@ struct kvm_tdx_cpuid_config {
>   	__u32 edx;
>   };
>   
> +/* supported_gpaw */
> +#define TDX_CAP_GPAW_48	(1 << 0)
> +#define TDX_CAP_GPAW_52	(1 << 1)
> +
> +struct kvm_tdx_capabilities {
> +	__u64 attrs_fixed0;
> +	__u64 attrs_fixed1;
> +	__u64 xfam_fixed0;
> +	__u64 xfam_fixed1;
> +	__u32 supported_gpaw;
> +	__u32 padding;
> +	__u64 reserved[251];
> +
> +	__u32 nr_cpuid_configs;
> +	struct kvm_tdx_cpuid_config cpuid_configs[];
> +};
> +

I think you should use __DECLARE_FLEX_ARRAY().

It's already used in existing KVM UAPI header:

struct kvm_nested_state {
	...
        union {
                __DECLARE_FLEX_ARRAY(struct kvm_vmx_nested_state_data,
					 vmx);
                __DECLARE_FLEX_ARRAY(struct kvm_svm_nested_state_data,
					 svm);
        } data;
}

>   #endif /* _ASM_X86_KVM_H */
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 07a3f0f75f87..816ccdb4bc41 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -6,6 +6,7 @@
>   #include "capabilities.h"
>   #include "x86_ops.h"
>   #include "x86.h"
> +#include "mmu.h"
>   #include "tdx_arch.h"
>   #include "tdx.h"
>   
> @@ -55,6 +56,58 @@ struct tdx_info {
>   /* Info about the TDX module. */
>   static struct tdx_info *tdx_info;
>   
> +static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
> +{
> +	struct kvm_tdx_capabilities __user *user_caps;
> +	struct kvm_tdx_capabilities *caps = NULL;
> +	int ret = 0;
> +
> +	if (cmd->flags)
> +		return -EINVAL;

Add a comment?

	/* flags is reserved for future use */

> +
> +	caps = kmalloc(sizeof(*caps), GFP_KERNEL);
> +	if (!caps)
> +		return -ENOMEM;
> +
> +	user_caps = (void __user *)cmd->data;
> +	if (copy_from_user(caps, user_caps, sizeof(*caps))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (caps->nr_cpuid_configs < tdx_info->num_cpuid_config) {
> +		ret = -E2BIG;
> +		goto out;
> +	}
> +
> +	*caps = (struct kvm_tdx_capabilities) {
> +		.attrs_fixed0 = tdx_info->attributes_fixed0,
> +		.attrs_fixed1 = tdx_info->attributes_fixed1,
> +		.xfam_fixed0 = tdx_info->xfam_fixed0,
> +		.xfam_fixed1 = tdx_info->xfam_fixed1,
> +		.supported_gpaw = TDX_CAP_GPAW_48 |
> +		((kvm_get_shadow_phys_bits() >= 52 &&
> +		  cpu_has_vmx_ept_5levels()) ? TDX_CAP_GPAW_52 : 0),
> +		.nr_cpuid_configs = tdx_info->num_cpuid_config,
> +		.padding = 0,
> +	};
> +
> +	if (copy_to_user(user_caps, caps, sizeof(*caps))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}

Add an empty line.

> +	if (copy_to_user(user_caps->cpuid_configs, &tdx_info->cpuid_configs,
> +			 tdx_info->num_cpuid_config *
> +			 sizeof(tdx_info->cpuid_configs[0]))) {
> +		ret = -EFAULT;
> +	}

I think the '{ }' is needed here.

> +
> +out:
> +	/* kfree() accepts NULL. */
> +	kfree(caps);
> +	return ret;
> +}
> +
>   int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
>   {
>   	struct kvm_tdx_cmd tdx_cmd;
> @@ -68,6 +121,9 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
>   	mutex_lock(&kvm->lock);
>   
>   	switch (tdx_cmd.id) {
> +	case KVM_TDX_CAPABILITIES:
> +		r = tdx_get_capabilities(&tdx_cmd);
> +		break;
>   	default:
>   		r = -EINVAL;
>   		goto out;
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index 473013265bd8..22c0b57f69ca 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -3,6 +3,9 @@
>   #define __KVM_X86_TDX_H
>   
>   #ifdef CONFIG_INTEL_TDX_HOST
> +
> +#include "tdx_ops.h"
> +

It appears "tdx_ops.h" is used for making SEAMCALLs.

I don't see this patch uses any SEAMCALL so I am wondering whether this 
chunk is needed here?

>   struct kvm_tdx {
>   	struct kvm kvm;
>   	/* TDX specific members follow. */